Redundancy in many types of systems is provided in order to increase reliability. For example, for a system complex run by a controller, system availability can be greatly improved if the controller can be made redundant. A controller in a server system may perform functions such as powering on/off and configuring the system, as well as communicating setup and status information to processor, memory and input/output (I/O) elements. Failure of such a controller would make the server system inoperable.
To implement redundant controllers a selection mechanism is required to determine which controller will be active controller in charge of the device or system under control, and which controller is idle controller waiting as backup. The selection mechanism or arbitration function is complicated in an environment where the outputs of the redundant controllers are to be electrically connected together externally and provided as input to a device/system under control.
Applicants recognize that in such an environment, the design implementation should ensure that the outputs of the redundant controllers are not capable of being enabled at the same instance in time in order to avoid possible conflicting data or potential damage to the device under control. The present invention is directed to providing a mechanism to address these arbitration needs within the noted environment where outputs controlled by redundant controllers are electrically connected together and provided as input to the device under control.